Refactor / restructure the RSS code into generic, IPv4 and IPv6 specific

bits.

The motivation here is to eventually teach netisr and potentially
other networking subsystems a bit more about how RSS work queues / buckets
are configured so things have a hope of auto-configuring in the future.

* net/rss_config.[ch] takes care of the generic bits for doing
  configuration, hash function selection, etc;
* topelitz.[ch] is now in net/ rather than netinet/;
* (and would be in libkern if it didn't directly include RSS_KEYSIZE;
  that's a later thing to fix up.)
* netinet/in_rss.[ch] now just contains the IPv4 specific methods;
* and netinet/in6_rss.[ch] now just contains the IPv6 specific methods.

This should have no functional impact on anyone currently using
the RSS support.

Differential Revision:	D1383
Reviewed by:	gnn, jfv (intel driver bits)

5 files changed, 780 insertions, 1 deletions

diff --git a/sys/net/if_ethersubr.c b/sys/net/if_ethersubr.c
index 9ba1f63..7227788 100644
--- a/sys/net/if_ethersubr.c
+++ b/sys/net/if_ethersubr.c
@@ -63,6 +63,7 @@
 #include <net/if_vlan_var.h>
 #include <net/if_llatbl.h>
 #include <net/pfil.h>
+#include <net/rss_config.h>
 #include <net/vnet.h>
 
 #include <netpfil/pf/pf_mtag.h>
@@ -71,7 +72,6 @@
 #include <netinet/in.h>
 #include <netinet/in_var.h>
 #include <netinet/if_ether.h>
-#include <netinet/in_rss.h>
 #include <netinet/ip_carp.h>
 #include <netinet/ip_var.h>
 #endif
diff --git a/sys/net/rss_config.c b/sys/net/rss_config.c
new file mode 100644
index 0000000..55f4952
--- /dev/null
+++ b/sys/net/rss_config.c
@@ -0,0 +1,558 @@
+/*-
+ * Copyright (c) 2010-2011 Juniper Networks, Inc.
+ * All rights reserved.
+ *
+ * This software was developed by Robert N. M. Watson under contract
+ * to Juniper Networks, Inc.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+
+__FBSDID("$FreeBSD$");
+
+#include "opt_inet6.h"
+#include "opt_pcbgroup.h"
+
+#ifndef PCBGROUP
+#error "options RSS depends on options PCBGROUP"
+#endif
+
+#include <sys/param.h>
+#include <sys/mbuf.h>
+#include <sys/socket.h>
+#include <sys/priv.h>
+#include <sys/kernel.h>
+#include <sys/smp.h>
+#include <sys/sysctl.h>
+#include <sys/sbuf.h>
+
+#include <net/if.h>
+#include <net/if_var.h>
+#include <net/netisr.h>
+#include <net/rss_config.h>
+#include <net/toeplitz.h>
+
+#if 0
+#include <netinet/in.h>
+#include <netinet/in_pcb.h>
+#include <netinet/in_rss.h>
+#include <netinet/in_var.h>
+
+/* for software rss hash support */
+#include <netinet/ip.h>
+#include <netinet/tcp.h>
+#include <netinet/udp.h>
+#endif
+
+/*-
+ * Operating system parts of receiver-side scaling (RSS), which allows
+ * network cards to direct flows to particular receive queues based on hashes
+ * of header tuples.  This implementation aligns RSS buckets with connection
+ * groups at the TCP/IP layer, so each bucket is associated with exactly one
+ * group.  As a result, the group lookup structures (and lock) should have an
+ * effective affinity with exactly one CPU.
+ *
+ * Network device drivers needing to configure RSS will query this framework
+ * for parameters, such as the current RSS key, hashing policies, number of
+ * bits, and indirection table mapping hashes to buckets and CPUs.  They may
+ * provide their own supplementary information, such as queue<->CPU bindings.
+ * It is the responsibility of the network device driver to inject packets
+ * into the stack on as close to the right CPU as possible, if playing by RSS
+ * rules.
+ *
+ * TODO:
+ *
+ * - Synchronization for rss_key and other future-configurable parameters.
+ * - Event handler drivers can register to pick up RSS configuration changes.
+ * - Should we allow rss_basecpu to be configured?
+ * - Randomize key on boot.
+ * - IPv6 support.
+ * - Statistics on how often there's a misalignment between hardware
+ *   placement and pcbgroup expectations.
+ */
+
+SYSCTL_DECL(_net_inet);
+SYSCTL_NODE(_net_inet, OID_AUTO, rss, CTLFLAG_RW, 0, "Receive-side steering");
+
+/*
+ * Toeplitz is the only required hash function in the RSS spec, so use it by
+ * default.
+ */
+static u_int	rss_hashalgo = RSS_HASH_TOEPLITZ;
+SYSCTL_INT(_net_inet_rss, OID_AUTO, hashalgo, CTLFLAG_RDTUN, &rss_hashalgo, 0,
+    "RSS hash algorithm");
+
+/*
+ * Size of the indirection table; at most 128 entries per the RSS spec.  We
+ * size it to at least 2 times the number of CPUs by default to allow useful
+ * rebalancing.  If not set explicitly with a loader tunable, we tune based
+ * on the number of CPUs present.
+ *
+ * XXXRW: buckets might be better to use for the tunable than bits.
+ */
+static u_int	rss_bits;
+SYSCTL_INT(_net_inet_rss, OID_AUTO, bits, CTLFLAG_RDTUN, &rss_bits, 0,
+    "RSS bits");
+
+static u_int	rss_mask;
+SYSCTL_INT(_net_inet_rss, OID_AUTO, mask, CTLFLAG_RD, &rss_mask, 0,
+    "RSS mask");
+
+static const u_int	rss_maxbits = RSS_MAXBITS;
+SYSCTL_INT(_net_inet_rss, OID_AUTO, maxbits, CTLFLAG_RD,
+    __DECONST(int *, &rss_maxbits), 0, "RSS maximum bits");
+
+/*
+ * RSS's own count of the number of CPUs it could be using for processing.
+ * Bounded to 64 by RSS constants.
+ */
+static u_int	rss_ncpus;
+SYSCTL_INT(_net_inet_rss, OID_AUTO, ncpus, CTLFLAG_RD, &rss_ncpus, 0,
+    "Number of CPUs available to RSS");
+
+#define	RSS_MAXCPUS	(1 << (RSS_MAXBITS - 1))
+static const u_int	rss_maxcpus = RSS_MAXCPUS;
+SYSCTL_INT(_net_inet_rss, OID_AUTO, maxcpus, CTLFLAG_RD,
+    __DECONST(int *, &rss_maxcpus), 0, "RSS maximum CPUs that can be used");
+
+/*
+ * Variable exists just for reporting rss_bits in a user-friendly way.
+ */
+static u_int	rss_buckets;
+SYSCTL_INT(_net_inet_rss, OID_AUTO, buckets, CTLFLAG_RD, &rss_buckets, 0,
+    "RSS buckets");
+
+/*
+ * Base CPU number; devices will add this to all CPU numbers returned by the
+ * RSS indirection table.  Currently unmodifable in FreeBSD.
+ */
+static const u_int	rss_basecpu;
+SYSCTL_INT(_net_inet_rss, OID_AUTO, basecpu, CTLFLAG_RD,
+    __DECONST(int *, &rss_basecpu), 0, "RSS base CPU");
+
+/*
+ * RSS secret key, intended to prevent attacks on load-balancing.  Its
+ * effectiveness may be limited by algorithm choice and available entropy
+ * during the boot.
+ *
+ * XXXRW: And that we don't randomize it yet!
+ *
+ * This is the default Microsoft RSS specification key which is also
+ * the Chelsio T5 firmware default key.
+ */
+static uint8_t rss_key[RSS_KEYSIZE] = {
+	0x6d, 0x5a, 0x56, 0xda, 0x25, 0x5b, 0x0e, 0xc2,
+	0x41, 0x67, 0x25, 0x3d, 0x43, 0xa3, 0x8f, 0xb0,
+	0xd0, 0xca, 0x2b, 0xcb, 0xae, 0x7b, 0x30, 0xb4,
+	0x77, 0xcb, 0x2d, 0xa3, 0x80, 0x30, 0xf2, 0x0c,
+	0x6a, 0x42, 0xb7, 0x3b, 0xbe, 0xac, 0x01, 0xfa,
+};
+
+/*
+ * RSS hash->CPU table, which maps hashed packet headers to particular CPUs.
+ * Drivers may supplement this table with a seperate CPU<->queue table when
+ * programming devices.
+ */
+struct rss_table_entry {
+	uint8_t		rte_cpu;	/* CPU affinity of bucket. */
+};
+static struct rss_table_entry	rss_table[RSS_TABLE_MAXLEN];
+
+static void
+rss_init(__unused void *arg)
+{
+	u_int i;
+	u_int cpuid;
+
+	/*
+	 * Validate tunables, coerce to sensible values.
+	 */
+	switch (rss_hashalgo) {
+	case RSS_HASH_TOEPLITZ:
+	case RSS_HASH_NAIVE:
+		break;
+
+	default:
+		printf("%s: invalid RSS hashalgo %u, coercing to %u",
+		    __func__, rss_hashalgo, RSS_HASH_TOEPLITZ);
+		rss_hashalgo = RSS_HASH_TOEPLITZ;
+	}
+
+	/*
+	 * Count available CPUs.
+	 *
+	 * XXXRW: Note incorrect assumptions regarding contiguity of this set
+	 * elsewhere.
+	 */
+	rss_ncpus = 0;
+	for (i = 0; i <= mp_maxid; i++) {
+		if (CPU_ABSENT(i))
+			continue;
+		rss_ncpus++;
+	}
+	if (rss_ncpus > RSS_MAXCPUS)
+		rss_ncpus = RSS_MAXCPUS;
+
+	/*
+	 * Tune RSS table entries to be no less than 2x the number of CPUs
+	 * -- unless we're running uniprocessor, in which case there's not
+	 * much point in having buckets to rearrange for load-balancing!
+	 */
+	if (rss_ncpus > 1) {
+		if (rss_bits == 0)
+			rss_bits = fls(rss_ncpus - 1) + 1;
+
+		/*
+		 * Microsoft limits RSS table entries to 128, so apply that
+		 * limit to both auto-detected CPU counts and user-configured
+		 * ones.
+		 */
+		if (rss_bits == 0 || rss_bits > RSS_MAXBITS) {
+			printf("%s: RSS bits %u not valid, coercing to  %u",
+			    __func__, rss_bits, RSS_MAXBITS);
+			rss_bits = RSS_MAXBITS;
+		}
+
+		/*
+		 * Figure out how many buckets to use; warn if less than the
+		 * number of configured CPUs, although this is not a fatal
+		 * problem.
+		 */
+		rss_buckets = (1 << rss_bits);
+		if (rss_buckets < rss_ncpus)
+			printf("%s: WARNING: rss_buckets (%u) less than "
+			    "rss_ncpus (%u)\n", __func__, rss_buckets,
+			    rss_ncpus);
+		rss_mask = rss_buckets - 1;
+	} else {
+		rss_bits = 0;
+		rss_buckets = 1;
+		rss_mask = 0;
+	}
+
+	/*
+	 * Set up initial CPU assignments: round-robin by default.
+	 */
+	cpuid = CPU_FIRST();
+	for (i = 0; i < rss_buckets; i++) {
+		rss_table[i].rte_cpu = cpuid;
+		cpuid = CPU_NEXT(cpuid);
+	}
+
+	/*
+	 * Randomize rrs_key.
+	 *
+	 * XXXRW: Not yet.  If nothing else, will require an rss_isbadkey()
+	 * loop to check for "bad" RSS keys.
+	 */
+}
+SYSINIT(rss_init, SI_SUB_SOFTINTR, SI_ORDER_SECOND, rss_init, NULL);
+
+static uint32_t
+rss_naive_hash(u_int keylen, const uint8_t *key, u_int datalen,
+    const uint8_t *data)
+{
+	uint32_t v;
+	u_int i;
+
+	v = 0;
+	for (i = 0; i < keylen; i++)
+		v += key[i];
+	for (i = 0; i < datalen; i++)
+		v += data[i];
+	return (v);
+}
+
+uint32_t
+rss_hash(u_int datalen, const uint8_t *data)
+{
+ 
+	switch (rss_hashalgo) {
+	case RSS_HASH_TOEPLITZ:
+		return (toeplitz_hash(sizeof(rss_key), rss_key, datalen,
+		    data));
+
+	case RSS_HASH_NAIVE:
+		return (rss_naive_hash(sizeof(rss_key), rss_key, datalen,
+		    data));
+
+	default:
+		panic("%s: unsupported/unknown hashalgo %d", __func__,
+		    rss_hashalgo);
+	}
+}
+
+/*
+ * Query the number of RSS bits in use.
+ */
+u_int
+rss_getbits(void)
+{
+
+	return (rss_bits);
+}
+
+/*
+ * Query the RSS bucket associated with an RSS hash.
+ */
+u_int
+rss_getbucket(u_int hash)
+{
+
+	return (hash & rss_mask);
+}
+
+/*
+ * Query the RSS layer bucket associated with the given
+ * entry in the RSS hash space.
+ *
+ * The RSS indirection table is 0 .. rss_buckets-1,
+ * covering the low 'rss_bits' of the total 128 slot
+ * RSS indirection table.  So just mask off rss_bits and
+ * return that.
+ *
+ * NIC drivers can then iterate over the 128 slot RSS
+ * indirection table and fetch which RSS bucket to
+ * map it to.  This will typically be a CPU queue
+ */
+u_int
+rss_get_indirection_to_bucket(u_int index)
+{
+
+	return (index & rss_mask);
+}
+
+/*
+ * Query the RSS CPU associated with an RSS bucket.
+ */
+u_int
+rss_getcpu(u_int bucket)
+{
+
+	return (rss_table[bucket].rte_cpu);
+}
+
+/*
+ * netisr CPU affinity lookup given just the hash and hashtype.
+ */
+u_int
+rss_hash2cpuid(uint32_t hash_val, uint32_t hash_type)
+{
+
+	switch (hash_type) {
+	case M_HASHTYPE_RSS_IPV4:
+	case M_HASHTYPE_RSS_TCP_IPV4:
+	case M_HASHTYPE_RSS_UDP_IPV4:
+	case M_HASHTYPE_RSS_IPV6:
+	case M_HASHTYPE_RSS_TCP_IPV6:
+	case M_HASHTYPE_RSS_UDP_IPV6:
+		return (rss_getcpu(rss_getbucket(hash_val)));
+	default:
+		return (NETISR_CPUID_NONE);
+	}
+}
+
+/*
+ * Query the RSS bucket associated with the given hash value and
+ * type.
+ */
+int
+rss_hash2bucket(uint32_t hash_val, uint32_t hash_type, uint32_t *bucket_id)
+{
+
+	switch (hash_type) {
+	case M_HASHTYPE_RSS_IPV4:
+	case M_HASHTYPE_RSS_TCP_IPV4:
+	case M_HASHTYPE_RSS_UDP_IPV4:
+	case M_HASHTYPE_RSS_IPV6:
+	case M_HASHTYPE_RSS_TCP_IPV6:
+	case M_HASHTYPE_RSS_UDP_IPV6:
+		*bucket_id = rss_getbucket(hash_val);
+		return (0);
+	default:
+		return (-1);
+	}
+}
+
+/*
+ * netisr CPU affinity lookup routine for use by protocols.
+ */
+struct mbuf *
+rss_m2cpuid(struct mbuf *m, uintptr_t source, u_int *cpuid)
+{
+
+	M_ASSERTPKTHDR(m);
+	*cpuid = rss_hash2cpuid(m->m_pkthdr.flowid, M_HASHTYPE_GET(m));
+	return (m);
+}
+
+int
+rss_m2bucket(struct mbuf *m, uint32_t *bucket_id)
+{
+
+	M_ASSERTPKTHDR(m);
+
+	return(rss_hash2bucket(m->m_pkthdr.flowid, M_HASHTYPE_GET(m),
+	    bucket_id));
+}
+
+/*
+ * Query the RSS hash algorithm.
+ */
+u_int
+rss_gethashalgo(void)
+{
+
+	return (rss_hashalgo);
+}
+
+/*
+ * Query the current RSS key; likely to be used by device drivers when
+ * configuring hardware RSS.  Caller must pass an array of size RSS_KEYSIZE.
+ *
+ * XXXRW: Perhaps we should do the accept-a-length-and-truncate thing?
+ */
+void
+rss_getkey(uint8_t *key)
+{
+
+	bcopy(rss_key, key, sizeof(rss_key));
+}
+
+/*
+ * Query the number of buckets; this may be used by both network device
+ * drivers, which will need to populate hardware shadows of the software
+ * indirection table, and the network stack itself (such as when deciding how
+ * many connection groups to allocate).
+ */
+u_int
+rss_getnumbuckets(void)
+{
+
+	return (rss_buckets);
+}
+
+/*
+ * Query the number of CPUs in use by RSS; may be useful to device drivers
+ * trying to figure out how to map a larger number of CPUs into a smaller
+ * number of receive queues.
+ */
+u_int
+rss_getnumcpus(void)
+{
+
+	return (rss_ncpus);
+}
+
+/*
+ * Return the supported RSS hash configuration.
+ *
+ * NICs should query this to determine what to configure in their redirection
+ * matching table.
+ */
+inline u_int
+rss_gethashconfig(void)
+{
+
+	/* Return 4-tuple for TCP; 2-tuple for others */
+	/*
+	 * UDP may fragment more often than TCP and thus we'll end up with
+	 * NICs returning 2-tuple fragments.
+	 * udp_init() and udplite_init() both currently initialise things
+	 * as 2-tuple.
+	 * So for now disable UDP 4-tuple hashing until all of the other
+	 * pieces are in place.
+	 */
+	return (
+	    RSS_HASHTYPE_RSS_IPV4
+	|    RSS_HASHTYPE_RSS_TCP_IPV4
+	|    RSS_HASHTYPE_RSS_IPV6
+	|    RSS_HASHTYPE_RSS_TCP_IPV6
+	|    RSS_HASHTYPE_RSS_IPV6_EX
+	|    RSS_HASHTYPE_RSS_TCP_IPV6_EX
+#if 0
+	|    RSS_HASHTYPE_RSS_UDP_IPV4
+	|    RSS_HASHTYPE_RSS_UDP_IPV4_EX
+	|    RSS_HASHTYPE_RSS_UDP_IPV6
+	|    RSS_HASHTYPE_RSS_UDP_IPV6_EX
+#endif
+	);
+}
+
+/*
+ * XXXRW: Confirm that sysctl -a won't dump this keying material, don't want
+ * it appearing in debugging output unnecessarily.
+ */
+static int
+sysctl_rss_key(SYSCTL_HANDLER_ARGS)
+{
+	uint8_t temp_rss_key[RSS_KEYSIZE];
+	int error;
+
+	error = priv_check(req->td, PRIV_NETINET_HASHKEY);
+	if (error)
+		return (error);
+
+	bcopy(rss_key, temp_rss_key, sizeof(temp_rss_key));
+	error = sysctl_handle_opaque(oidp, temp_rss_key,
+	    sizeof(temp_rss_key), req);
+	if (error)
+		return (error);
+	if (req->newptr != NULL) {
+		/* XXXRW: Not yet. */
+		return (EINVAL);
+	}
+	return (0);
+}
+SYSCTL_PROC(_net_inet_rss, OID_AUTO, key,
+    CTLTYPE_OPAQUE | CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, 0, sysctl_rss_key,
+    "", "RSS keying material");
+
+static int
+sysctl_rss_bucket_mapping(SYSCTL_HANDLER_ARGS)
+{
+	struct sbuf *sb;
+	int error;
+	int i;
+
+	error = 0;
+	error = sysctl_wire_old_buffer(req, 0);
+	if (error != 0)
+		return (error);
+	sb = sbuf_new_for_sysctl(NULL, NULL, 512, req);
+	if (sb == NULL)
+		return (ENOMEM);
+	for (i = 0; i < rss_buckets; i++) {
+		sbuf_printf(sb, "%s%d:%d", i == 0 ? "" : " ",
+		    i,
+		    rss_getcpu(i));
+	}
+	error = sbuf_finish(sb);
+	sbuf_delete(sb);
+
+	return (error);
+}
+SYSCTL_PROC(_net_inet_rss, OID_AUTO, bucket_mapping,
+    CTLTYPE_STRING | CTLFLAG_RD, NULL, 0,
+    sysctl_rss_bucket_mapping, "", "RSS bucket -> CPU mapping");
diff --git a/sys/net/rss_config.h b/sys/net/rss_config.h
new file mode 100644
index 0000000..37d82ae
--- /dev/null
+++ b/sys/net/rss_config.h
@@ -0,0 +1,123 @@
+/*-
+ * Copyright (c) 2010-2011 Juniper Networks, Inc.
+ * All rights reserved.
+ *
+ * This software was developed by Robert N. M. Watson under contract
+ * to Juniper Networks, Inc.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+#ifndef _NET_RSS_CONFIG_H_
+#define	_NET_RSS_CONFIG_H_
+
+#include <netinet/in.h>		/* in_addr_t */
+
+/*
+ * Supported RSS hash functions.
+ */
+#define	RSS_HASH_NAIVE		0x00000001	/* Poor but fast hash. */
+#define	RSS_HASH_TOEPLITZ	0x00000002	/* Required by RSS. */
+#define	RSS_HASH_CRC32		0x00000004	/* Future; some NICs do it. */
+
+#define	RSS_HASH_MASK		(RSS_HASH_NAIVE | RSS_HASH_TOEPLITZ)
+
+/*
+ * Instances of struct inpcbinfo declare an RSS hash type indicating what
+ * header fields are covered.
+ */
+#define	RSS_HASHFIELDS_NONE		0
+#define	RSS_HASHFIELDS_4TUPLE		1
+#define	RSS_HASHFIELDS_2TUPLE		2
+
+/*
+ * Define RSS representations of the M_HASHTYPE_* values, representing
+ * which particular bits are supported.  The NICs can then use this to
+ * calculate which hash types to enable and which not to enable.
+ *
+ * The fact that these line up with M_HASHTYPE_* is not to be relied
+ * upon.
+ */
+#define	RSS_HASHTYPE_RSS_IPV4		(1 << 1)	/* IPv4 2-tuple */
+#define	RSS_HASHTYPE_RSS_TCP_IPV4	(1 << 2)	/* TCPv4 4-tuple */
+#define	RSS_HASHTYPE_RSS_IPV6		(1 << 3)	/* IPv6 2-tuple */
+#define	RSS_HASHTYPE_RSS_TCP_IPV6	(1 << 4)	/* TCPv6 4-tuple */
+#define	RSS_HASHTYPE_RSS_IPV6_EX	(1 << 5)	/* IPv6 2-tuple + ext hdrs */
+#define	RSS_HASHTYPE_RSS_TCP_IPV6_EX	(1 << 6)	/* TCPv6 4-tiple + ext hdrs */
+#define	RSS_HASHTYPE_RSS_UDP_IPV4	(1 << 7)	/* IPv4 UDP 4-tuple */
+#define	RSS_HASHTYPE_RSS_UDP_IPV4_EX	(1 << 8)	/* IPv4 UDP 4-tuple + ext hdrs */
+#define	RSS_HASHTYPE_RSS_UDP_IPV6	(1 << 9)	/* IPv6 UDP 4-tuple */
+#define	RSS_HASHTYPE_RSS_UDP_IPV6_EX	(1 << 10)	/* IPv6 UDP 4-tuple + ext hdrs */
+
+/*
+ * Compile-time limits on the size of the indirection table.
+ */
+#define	RSS_MAXBITS	7
+#define	RSS_TABLE_MAXLEN	(1 << RSS_MAXBITS)
+
+/*
+ * Maximum key size used throughout.  It's OK for hardware to use only the
+ * first 16 bytes, which is all that's required for IPv4.
+ */
+#define	RSS_KEYSIZE	40
+
+/*
+ * For RSS hash methods that do a software hash on an mbuf, the packet
+ * direction (ingress / egress) is required.
+ *
+ * The default direction (INGRESS) is the "receive into the NIC" - ie,
+ * what the hardware is hashing on.
+ */
+#define	RSS_HASH_PKT_INGRESS	0
+#define	RSS_HASH_PKT_EGRESS	1
+
+/*
+ * Device driver interfaces to query RSS properties that must be programmed
+ * into hardware.
+ */
+u_int	rss_getbits(void);
+u_int	rss_getbucket(u_int hash);
+u_int	rss_get_indirection_to_bucket(u_int index);
+u_int	rss_getcpu(u_int bucket);
+void	rss_getkey(uint8_t *key);
+u_int	rss_gethashalgo(void);
+u_int	rss_getnumbuckets(void);
+u_int	rss_getnumcpus(void);
+u_int	rss_gethashconfig(void);
+
+/*
+ * Hash calculation functions.
+ */
+uint32_t	rss_hash(u_int datalen, const uint8_t *data);
+
+/*
+ * Network stack interface to query desired CPU affinity of a packet.
+ */
+struct mbuf * rss_m2cpuid(struct mbuf *m, uintptr_t source, u_int *cpuid);
+u_int	rss_hash2cpuid(uint32_t hash_val, uint32_t hash_type);
+int	rss_hash2bucket(uint32_t hash_val, uint32_t hash_type,
+	    uint32_t *bucket_id);
+int	rss_m2bucket(struct mbuf *m, uint32_t *bucket_id);
+
+#endif /* !_NET_RSS_CONFIG_H_ */
diff --git a/sys/net/toeplitz.c b/sys/net/toeplitz.c
new file mode 100644
index 0000000..4328ec4
--- /dev/null
+++ b/sys/net/toeplitz.c
@@ -0,0 +1,58 @@
+/*-
+ * Copyright (c) 2010 David Malone <dwmalone@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/types.h>
+
+#include <net/rss_config.h>
+#include <net/toeplitz.h>
+
+#include <sys/systm.h>
+
+uint32_t
+toeplitz_hash(u_int keylen, const uint8_t *key, u_int datalen,
+    const uint8_t *data)
+{
+	uint32_t hash = 0, v;
+	u_int i, b;
+
+	/* XXXRW: Perhaps an assertion about key length vs. data length? */
+
+	v = (key[0]<<24) + (key[1]<<16) + (key[2] <<8) + key[3];
+	for (i = 0; i < datalen; i++) {
+		for (b = 0; b < 8; b++) {
+			if (data[i] & (1<<(7-b)))
+				hash ^= v;
+			v <<= 1;
+			if ((i + 4) < RSS_KEYSIZE &&
+			    (key[i+4] & (1<<(7-b))))
+				v |= 1;
+		}
+	}
+	return (hash);
+}
diff --git a/sys/net/toeplitz.h b/sys/net/toeplitz.h
new file mode 100644
index 0000000..135e5b9
--- /dev/null
+++ b/sys/net/toeplitz.h
@@ -0,0 +1,40 @@
+/*-
+ * Copyright (c) 2010 David Malone <dwmalone@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+#ifndef _NETINET_TOEPLITZ_H_
+#define	_NETINET_TOEPLITZ_H_
+
+/*
+ * Toeplitz (RSS) hash algorithm; possibly we should cache intermediate
+ * results between runs, in which case we'll need explicit init/destroy and
+ * state management.
+ */
+uint32_t	toeplitz_hash(u_int keylen, const uint8_t *key,
+		    u_int datalen, const uint8_t *data);
+
+#endif /* !_NETINET_TOEPLITZ_H_ */